D.4.7 Linked List Algorithms with Object References Notes

public class LinkedList{
	public static class Node{ // ideally in seperate file
		public int value;
		public Node next;
		public Node(int valueIn){ // constructor with passed value
			this.value = valueIn;
			this.next = null;
		}
	}
	
	private Node head; // default null
	
	public void print(){ // iterate through list and output values
		String res = "";
		if (this.head == null){
			System.out.println("List is empty");
			return; // stop method execution
		}
		Node currentNode = this.head;
		while (currentNode != null){ // iterate through
			res += currentNode.value + " ";
			currentNode = currentNode.next; // move on to the next node
		}
		System.out.println(res);
	}
	
	
	public void add(int newValue){
			Node newNode = new Node(newValue);
			// insertion at the beginning
			if (this.head == null){ // if list is empty
				this.head = newNode; // move head pointer
				return; // stop method execution
			}
			if (this.head.value > newValue){ // if new value is smaller then it is still insertion at the beginning, but newNode's next should be updated
				newNode.next = this.head;
				this.head = newNode;
				return; // stop method execution
			}
			
			
			// insertion in the order in the middle
			Node currentNode = this.head;
			while (currentNode.next != null){ // iterate through until last
					if (currentNode.next.value > newValue){ // (currentNode.next).value 
						// position found
						Node temp = currentNode.next;
						currentNode.next = newNode;
						newNode.next = temp;
						return; // stop method execuiton as action was completed
					} else {
						currentNode = currentNode.next; // move on to the next node
					}
			}
			// if newNode should be added to the end, then code here is executed
			// here currentNode is the last node (after iteration above)
			currentNode.next = newNode;
	}
	
	
	public void delete(int valueOut){
		if (this.head == null){// if list is empty stop method execution
			return;
		}
		if (this.head.value == valueOut){ // if value to remove is at the beginning
			this.head = this.head.next; // move reference to next node
			return; // stop method execution
		}
		
		Node currentNode = this.head; // already skip the element at the beginning as we compared it before
		while (currentNode.next != null){ // iterate through whole list except last element
			Node nextNode = currentNode.next;
			if (nextNode.value == valueOut){ // if next node is node that we need to delete
				currentNode.next = nextNode.next; // skip node
				return; // stop method execution
			}
			currentNode = currentNode.next; // move to next node
		}
		
		System.out.println("Element not found");
	}
	
	public boolean isEmpty(){
		return this.head == null; // returns true is head is empty (no elements)
		
	}
	public static void main(String[] args){ // test the code
		LinkedList myList = new LinkedList();
		// test isEmpty() when empty
		System.out.println(myList.isEmpty());
		// test add()
		int[] values = {5, 2, 6, 3, 1, 10, 7, 9, 8, 4};
		for (int i : values){ // for i in values
				myList.add(i);
		}
		myList.print(); // output list
		// test isEmpty() when non-empty
		System.out.println(myList.isEmpty());
		// test delete()
		myList.delete(1);
		myList.print();
		myList.delete(4);
		myList.print();
		myList.delete(10);
		myList.print();
	}
}